ECONOMIC GEOLOGY. 
65 
Nupuchondzo and elsewhere in the lower Nyang Chu valley. At 
Lhasa the prevailing rocks are granite and Jurassic slate and quart- 
zite, with no trace of carbonaceous beds, while the fuel employed 
in the local " arsenal " was found to be not coal — as had been 
reported — but charcoal. Some quantity of graphite was found in this 
building^, beinof used for the manufacture of 
Graphite. 
crucibles, and I am indebted to Mr. E. C. Wilton, 
C.M.G., Assistant to the British Commissioner, for samples of the 
mineral, and also for the suggestion that it represents the so-called 
" coal." The graphite is said to come from the Rong valley between 
Yamdrok Tso and Shie^atse. The same valley 
Lead. ^ 
is also said to yield lead, but the report was not 
substantiated by any reliable evidence, 
While at Lhasa, I bought a number of samples of the gem-stones 
employed by the local jewellers ; these included 
Gem^stones. 
turquoise, ruby, tourmaline, emerald, and sapphire- 
The jewellers stated that all these stones were brought from consider- 
able distances, the turquoise being obtained from Ladaki and Mongolian 
traders, the rubies and emeralds from India and Mongolia, and the 
sapphires from Ladak and India. I could obtain no reliable informa- 
tion as to the existence of any indigenous source of gems. The 
rubies and emeralds were small and very pale ; the sapphires were, 
on the whole, of better quality, but small, often pale and flawed, and 
though a few stones of good colour were to be obtained, they were 
very small and of little value. Pink tourmaline is also apparently 
used largely, not being distinguished from ruby of similar colour. 
Yellow and white rock-crystal and red garnet are also used. It appears 
that, with the exception of turquoise, practically all the gem-stones 
used in Lhasa come from foreign countries, and it is not at all improb- 
able that quite a large proportion of them come from Ceylon and 
Burma, via Calcutta and Nepal. 
An efflorescence, composed chiefly of sodium carbonate, is found in 
„ ^, , the valley of the Yaru river near Utsi ; this is 
Sodium carbonate. •' 
collected and used by the Tibetans for various 
purposes, both industrial and culinary. 
( 186 ) 
